Conventionally, when portable telephones and automobile phones receive calls, beep sounds are produced to notify users (or subscribers) of reception of incoming calls. However, beep sounds are offensive to ears of the users, so recently sound source circuits are frequently provided inside of the portable telephones to produce melody sounds as incoming call sounds.
It is required that the sound source circuits used in small-size devices such as portable telephones be reduced in size and inexpensive in cost. For this reason, monophonic sound source circuits are normally used in the portable telephones. However, the monophonic sound source circuits only produce sounds that are monotonous and thin in sound quality. To cope with such disadvantages, it is possible to propose an idea in which chorus effects are imparted to sounds to provide rich sound quality. Conventionally, imparting chorus effects to sounds is implemented by using effectors (or effect devices) following the sound source circuits. However, the sound source circuits coupled with the effectors are complicated in configuration and expensive in cost. Therefore, it is impractical for engineers to employ the sound source circuits coupled with the effectors for use in the portable telephones.
It is an object of this invention to provide a sound source circuit and a telephone terminal using it by which chorus effects can be imparted to sounds for notifying users of reception of incoming calls with a simple and inexpensive configuration.